var Helper=(function() {
    var PTMRatio = 30.0,
        toWorld = function (n) {
            return n / PTMRatio;
        },
        toScreen = function (n) {
            return n * PTMRatio;
        };
        return{
            toWorld:function(n){
                return toWorld(n);
            },
            toScreen: function (n) {
            return toScreen(n);
            }
        };
}());


